Well, I learned something new today and to think I went to college for this kind of stuff.  I had never considered what curry powder was, so I looked it up.  Here's what I found.
There is no single recipe for curry powder. It was invented by the British in India as a quick substitute for the thousands of different spice blends Indian cooks make for themselves. A basic curry powder includes black pepper, chili, coriander, cumin, ginger and turmeric in varying proportions; it often has fenugreek and oily spices such as cardamom, cinnamon, cloves and mace, and can include cassia leaves, curry leaves, mustard and poppy seeds too. To make your own, experiment until you find a mixture you like.